I came across this issue recently when i tried to update one of my wordpress blogs that was lying idle for a long time. The version it was running was 4+ and i wanted to update it to the latest version.
WordPress offers manual and automatic updates. I choose the later from dashboard. The download of files went fine, but then stuck at unpacking with the message “Unpacking the update”.
I tried re-updating but came across another problem. Now WordPress would not allow me to run the update again and showed “another update in progress” message. WordPress has locked the previous update and would not allow further updates.
After some trial and error and googling i came up with a solution to both the problems.
To solve the update locked problem, install “Fix Another Update in Process” plugin from wordpress repository. Activate the plugin and go to its settings options to fix the update process.
Now you can restart the update process, but hold on! You will need to make some changes to your PHP configurations.
Open php.ini and make changes to the following lines
max_execution_time=120 // previously was 30
max_input_time=120 // previously was 60
upload_max_filesize=12M // previously was 2M
Now restart the server, and restart your WordPress update process. This time it will update smoothly!
Note that you can get access to server and php.ini file only if you are working on local development environment or have root access in production environment. In most cases people use shared hosting which does not allow for changing these values in php.ini. The only effective solution in that case is to contact hosting support and ask them to make changes if possible. Else you are stuck with doing manual updates file by file!